This invention relates in general to a system and method for minimizing damage to a building due to a fire originating in the roof of the building, the system having other advantages, and more particularly to a system and method for arresting a fire which may have started on the exterior roof surface, such as by a flying ember for example, before that fire produces significant damage.
While the invention has application in roofs fabricated from any flammable material, the invention is particularly useful in connection with wood shingle roofs.
Wood shingle roofs are hazardous in the event of a fire, because they are extremely flammable when dry, causing a rapid spread of a fire throughout a structure. For structures having a large expanse of wood shingle roof, the damage can be very great unless some means is provided to retard the spread of the fire along the roof. Wood shingle roofs represent a particular hazard where a number of neighboring homes have such roofs, particularly when such homes are erected in close proximity. In that situation, a fire in one structure may quickly spread to neighboring structures, through flying sparks or embers, particularly under high wind conditions. In these situations, a major fire fighting effort may be directed to saving adjacent structures, rather than minimizing damage at a primary fire which is already well advanced.
It has been observed that a fire starting at the exposed surface of a wood shingle roof, by an ember for example, will spread in a predetermined manner; and this invention is concerned with an automatic system for detecting such a fire at a very early stage and in extinguishing that fire before it can spread to any significant degree.
There are known in the prior art systems for dispensing water onto the exterior roof of a building, residence or otherwise, for the purpose of wetting down the roof to perhaps prevent a roof fire from being ignited by flying embers or sparks in the event of a nearby brush fire, forest fire or structure fire, for example. Such systems are disclosed in Thompson U.S. Pat. No. 1,620,142, Banzato U.S. Pat. No. 3,179,181, and McFadden U.S. Pat. No. 3,583,490. The latter two of these patents disclose systems for supplying the water from a source such as a swimming pool to dispensing means on the roof, including electric motor driven pumps which may be put into operation automatically in response to a detection system. The detection devices for these systems are thermostats which are responsive to the heat of flame and it is thought that these may be placed on or about the structure in any desired manner. A difficulty with thermostats, particularly if there are a relatively few thermostats spaced over a relatively large roof area, is that they will likely not be responsive to a fire until it has been well established, except in the situation of course where the fire may start at the precise location of one thermostat. The placing of a sufficiently large number of thermostats to detect a small fire before it has spread significantly presents problems of substantial expense with respect to both the cost of the thermostats themselves and to the costs for wiring up a substantial number of thermostats. Another difficulty with such systems is that if a fire destroys the wiring before detection is accomplished, the system is rendered inoperative. Another difficulty with such system, particularly where relatively few thermostats are used, is that the fire may not be detected until it is well established and the established fire may rupture the water supply system before it has been effective to wet the roof surface. A major problem in connection with roof protection systems then is to provide a sensing device or system which is effective to detect a small fire at any location on the roof surface and before it has spread significantly, and to activate the water dispensing system to extinguish the fire before it has advanced to the extent that it may render inoperative either the detection system or the water dispensing system. The above mentioned prior art patents do not suggest a practical solution to that problem.
A further problem with the provision of a practical detection system for detecting fires on the exterior roof surface is that the detection devices or systems should most advantageously be placed on that exterior roof surface. This means that the detection devices or systems must have the capability of withstanding various deteriorating conditions and incidents, and still maintain reliability. Foremost among these conditions are the elements: sun, wind, rain, sleet, ice and snow. A condition with wood shingle roofs that results from the elements is that the shingles buckle and crack with time. The system must be resistant to materials which may be deposited on roofs such as leaves, nuts falling from trees, and other blowing plant material and debris which drops from trees or other vegetation. Further the detection devices or systems must be resistant to the activities of animals which move about roofs and also to humans who have occasion to be on roofs for various service and maintenance purposes.
One object of this invention is to provide a system and method for preventing or retarding the spread of fires which originate at the exposed surface of a roof.
A further object of this invention is to provide a system and method for extinguishing very quickly a wood roof fire which has been started by an ember or a spark from a neighboring fire.
Still another object of this invention is to provide a system and method for detecting a fire in a building roof, and for effecting automatically an extinguishing water flow.
A still further object of this invention is to provide a system and method for effectively detecting a small roof surface fire at any location on a wood shingle roof.
Another object of this invention is to provide a system for detecting very quickly a small fire in a wood shingle roof and for automatically initiating extinguishing water flow before the fire can spread significantly.
A further object of this invention is to provide a system for reducing the cost of cooling a residence or like building structure.
Still another object of this invention is to provide a system for minimizing the settling of a building foundation or floor slab.
A still further object of this invention is to provide a system for preventing the start of a roof fire by airborne sparks or embers.
Still another object of this invention is to provide an effective fire protection system for wood roof, which system can be installed at reasonable cost in either an existing or a new structure.
These objects are accomplished in a fire protection system which includes water dispensing means such as sprinkler heads mounted on the roof structure and above the exposed roof surface in a manner to effectively wet the entire roof surface either by direct spray or runoff. Feed pipe means feed water from a supply source, such as the water utility, to the dispensing means. A motorized gate valve connects the feed pipe to the supply source. A flame sensor circuit includes an electric current conductor disposed on the exposed roof surface and a signal device connected in an electrically energized circuit, with the signal device being triggered in response to a predetermined condition of the flame sensor circuit. A control circuit connects the signal device to the motorized valve, to effect the opening of the valve in response to the triggering of the signal device.
More particularly several of such flame sensor circuits may be provided each having an associated signal device, with all of the signal devices being connected by the control circuit to the motorized valve. Also more particularly a smoke sensor circuit includes a smoke sensitive device, disposed beneath the roof surface, and a second signal device, the signal device being triggered in response to detection of a selected smoke level. This second signal device is also connected by the control circuit to the motorized valve. Again several of said smoke sensor circuits may be provided.
Also more particularly the system may include an electric motor driven booster pump; and the control circuit may connect the several signal devices to the booster pump starting circuit to start the booster pump simultaneously with the opening of the motorized valve.
Still more particularly, the conductors of the flame sensor circuits are disposed in runs spaced at selected distances from each other, to be overrun quickly by a small roof fire.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.